A fast algal bioassay for assessment of copper toxicity in water using Euglena gracilis

Abstract

A rapid, sensitive algal bioassay was investigated to monitor copper toxicity using photosynthetic activity and motility parameters as end points in the photosynthetic flagellate Euglena gracilis. Effects on motility parameters were determined using the automatic bioassay ECOTOX. Photosynthetic efficiency was measured using chlorophyll fluorescence by means of a fast, noninvasive pulse amplitude modulated fluorometer. These parameters were assessed regarding their effectiveness as end points for short-(0-24 h) and long-term (1-5 days) toxicity tests. The model organism showed significant responses to the tested concentrations at both motility and photosynthesis examined levels. EC 50 values for movement parameters immediately after the cells were mixed with copper are 19.09 (300.4 μM), 20.4 (312 μM) and 23.09 (363.35 μM)mg L −1 for motility, rvalue and velocity, respectively. The current study proofs that Euglena is a convenient biotest organism where motility parameters show rapid sensitive responses to copper (direct exposure to copper). Also, the photosynthetic parameters appear to be appropriate for acute and chronic toxicity tests for higher and lower copper concentrations, respectively.

Environmental monitoring using bioassays

“…Fast responses could be observed either within hours or even during short-term incubation within minutes. Ahmed and Häder [26] defined end points for short tests after 0À24 h, and for long-term tests after 1À5 days. In a study by Pettersson and Ekelund [6] the shortterm tests were 3 min and the long-term tests were 7 days when studying the motility in Euglena gracilis.…”

“…Toxicity effects of the tested chemicals, even at low concentrations, can be obtained after 20 min of incubation [28]. The rapid techniques of pulse amplitude modulation (PAM) fluorometry [29] has a great advantage because it provides direct information on the photosynthetic activity of the algae, in comparison to measurements of cell numbers which requires several hours of incubation [7,26,30]. Other tests with microalgae and photosynthesis which are defined as short-term tests use 6 h to monitor and evaluate the toxic effects of metals [31].…”

Toxicity evaluation of copper and zinc cyanide complexes using Euglena gracilis Z and SMZ as an in-vivo model

“…Euglena gracilis has been introduced previously as a successful model as a bio-indicator in polluted areas (Einicker-Lamas et al 2002;Ahmed and Häder 2010). This alga possesses a remarkable metabolic plasticity.…”

“…The applicability of Euglena gracilis Z and SMZ strains as a bioanalytical model for assessing the toxicity of free and metal-cyanides was examined based on its demonstrated sensitivity as a unicellular tool used in several environmental toxicity assessments (Einicker-Lamas et al 1996;Einicker-Lamas et al 2002;Watanabe and Suzuki 2002;Ahmed and Häder 2010).…”

“…It is important to note that other algal cells would not tolerate acid conditions hence is not possible to stimulate the acidic stomach condition where toxic cyanide including metal-cyanide complexes may release upon exposure. In addition to the above mentioned unique characteristics, the low cost, easy culturing and rapid growing of Euglena gracilis fulfils the requirements as a bioassay organism (Ahmed and Häder 2010).…”